source of maintenance "headaches. " It was decided to 

 substitute a better designed motor and to increase their 

 number. Since the craft is not steerable at its low speeds, 

 it was also decided that it would be better to maneuver it 

 by force or thrust component rather than by trying to 

 "twist, " i. e. , going ahead on one motor and backing on the 

 other. Some difficulty was experienced in finding a U. S. 

 contractor willing to build suitable motors, but finally the 

 General Electric Company constructed six 3-hp, inert, 

 fluid-filled motors, five of which were mounted on the 

 bathyscaph. These motors are special 24-volt dc motors, 

 with rotors potted in epoxy plastic to reduce windage losses 

 and helical- cut commutators that provide a wiping action 

 at the brushes to prevent formation of insulating film at 

 that area. The motors operate in silicone oil. 



In service, the motors have proved to be efficient and 

 they provide excellent maneuverability for the craft at low 

 speeds. For maximum flexibility, two motors are mounted 

 in vertical tubes, one in each end tank to provide vertical 

 thrust, two are mounted as propulsion motors allowing 

 forward and aft movement, and one motor is mounted 

 athwartships for turning purposes. The motors drive 

 geared propellers, at approximately 300 rpm maximum 

 speed for the propulsion and turning motors and at 600 rpm 

 for the vertical thrust motor. A rheostat controller allows 

 regulation of the motor speed over about half of its rpm 

 range and, in addition, all motors can be reversed. 



7. LIGHTING 



The original lighting system on TRIESTE consisted of 

 four miniature mercury vapor lamps. One unit was located 

 forward, two above the sphere, and the fourth aft near the 

 fixed rudder. Each unit was designed to operate at 500 

 volts; however, many times in service the lamps would not 

 light with this voltage owing to their extreme temperature 

 sensitivity. The lamps were made by the Phillips Company 

 of Holland and were difficult to replace. The only readily 

 available mercury vapor lamps in the United States operate 

 at 1000 volts, thus causing wiring problems. 



Investigations made to solve the lighting problem are 

 the subject of a NEL report. 4 Two types of lighting were 



See footnote reference 2, page 19 



37 



